Dont know if this will help u, but i had the exact same problem and it was a game killer for me.
Well i play on a gamer laptop and it adjust the boost power on my GPU (and CPU) automatically, but i start to monitor the "GPU Mhz" on my G13 display when i was playing and found out that sometimes the game wont "wake up" the GPU.. And that causes the GPU to run at 135-200 Mhz.
It should run at max (770-850 Mhz) when a game is running..!
My GPU is a Geforce GTX 780M, so i looked at Nvidia Control Panel and set the parameters at full power ("Prefer Maximum Performance").
Since my system is Danish i wont write what it says, but look at someting like this in your Graphic Control Setting:
Manage 3D settings - "Prefer Maximum Performance" or similar.
For me it made the game alot more fun to play and i have no "suddenly " framedrops as i use to have!
I could imagine that it could help on a stationary as well on a laptop :-)
